In recent decades, there has been considerable progress in making electrocatalysts of Pt/C. These catalysts have been improved by the development of methods of dispersing Pt metal into 2-3 nm particles deposited on carbon supports.
For current commercial products, the level of Pt mass activity toward the oxygen reduction reaction (ORR) is approximately 0.08 A/mg Pt in Membrane Electrode Assembly (MEA) tests, and 0.1 A/mg Pt on Rotating Disk Electrode (RDE) tests at 0.9 V (iR free).
However, in order to meet the automotive-competitive (AC) target for Polymer Electrolyte Membrane (PEM) fuel cells for vehicle applications, the Pt mass activity toward the ORR of Pt-containing cathode catalysts must be increased by at least four to eight times over current state-of-the-art catalysts, without compromising catalyst durability.
One attempt to meet this target involves the use of alloy nanoparticles of Pt with 3d transition metal(s). Although these materials have been reported to increase Pt mass activity for ORR by two to three times, that is not sufficient to meet the goal.
Another approach toward improved ORR catalysts relies on the use of Pt monolayer catalysts. However, Pt monolayers are difficult to generate and can only be deposited on noble metal substrates, or on a non-noble metal substrate with a pre-existing noble-metal shell.
Therefore, there remains a need for an electrocatalyst which improves the Pt mass activity toward the ORR, and for methods of making such electrocatalysts.